Monit is a free open source utility for managing and monitoring, processes, programs, files, directories and filesystems on a UNIX system. Monit conducts automatic maintenance and repair and can execute meaningful causal actions in error situations. You can use Monit to monitor daemon processes or similar programs running on localhost. Monit is particular useful for monitoring daemon processes, such as those started at system boot time from /etc/init.d/.

Common monit usage:
a) Monit can start a process if it does not run.
b) Restart a process if it does not respond.
c) Stop a process if it uses to much resources etc.